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Is it easy to get a hygrometer to measure humidity with a guaranteed accuracy range?

Can anyone recommend a hygrometer where the manufacturer guarantees the accuracy to a stated range (maybe 1% or 2%)?

I'm not sure it would be useful or necessary to have a home hygrometer of that precision or accuracy. I would postulate that what you're really interested in is a humidification / dehumidification system that can maintain ambient humidity at a relatively constant level throughout the year. It's really the seasonal fluctuations that are responsible for issues associated with soundboard deterioration. You would most likely like to maintain room humidity at a constant level that's within 5% or so of what's personally comfortable, probably 30% or 40% or so.

Just an uneducated thought.

David-G,
See this web site. I would recommend sling psychrometers.

http://asd-www.larc.nasa.gov/SCOOL/psychrometer.html

Masaki

Sure. They're *VERY* expensive, need constant calibration, and break frequently.

I use this at work.
http://www.tequipment.net/AmprobeTHWD-2.asp?gclid=COy2-dS68ZICFQKLxwodmReh3w

I use Onset data loggers and software (called HOBOware) to record RH and temperature and plot the data on my computer. I have 3 units purchased over the course of a couple of years. The last time I checked placing them side by side on my piano, the spread in RH was about 1.5% . They are quite sensitive, when I have them connected to my laptop and just breath normally on them I can see the reading change.

Here is the link

I think it's important to have a reliable hygrometer, though as previously mentioned extreme accuracy is not necessary. But, based on my experience, the built-in hygrometers in some humidifiers are not reliable enough, they are affected by the placement of the humidifier in the room, and you can't place them where you really want to on or near the piano. That's why I like have separate data loggers.

Although some have scoffed, I have found the hygrometer-thermometer formerly sold by Radio Shack to be very satisfactory. When checked against other instruments, such as the very expensive one used by the plant engineer at the music conservatory, they have always been in good agreement. This model has been sold under other brand names. Sling psychrometers are expensive and somewhat fragile.

daft as it sounds try your local cigar merchant as well. Cigars require precise humidity levels to be kept at their best and you can pick up a digital hygrometer with thermometer very cheaply - western digital certainly make one for about £20 i believe.

thermometer-hygrometer by TFA 30.5002 about 29.00 euros, by LUFFT DTH 200 about 140.00 euros

alternatively purchase a Sauter M line piano with built in hygrometer hehe ?

There are also the MicroLog and MicroLog Pro dataloggers from Fourier Systems (www.fouriersystems.com). You can use these with a wireless cradle that allows you to collect data and manage the sensor units from a PC. (Sadly, there is no software for the Mac.)

Veriteq also makes a very good temp/RH data logger, which can be paired with a Digi Wifi mini-transmitter. This combo is the best, but very expensive.

RH sensors have to be calibrated regularly, typically once a year.

Edit: Onset's HOBO series of data loggers also has an Ethernet connectivity solution, but not wireless.

You can easily calibrate your hygrometer with table salt and water. Add water to salt in a cup to make a slurry, like wet sand. Put the cup in a sealed bag with your hygrometer for 8 -12 hours. The salt will maintain 75% relative humidity. When you read your hygrometer, you'll know how far off it is. All further readings can be adjusted by this value.

Many thanks to you all for your various suggestions, it will take me a little time to absorb all this information! If anyone else has any thoughts, please do post them.

Thanks again.